/**
 * http://mongodb.github.io/node-mongodb-native
 * http://mongodb.github.io/node-mongodb-native/3.0/api/
 */
//DB库
var MongoDB = require('mongodb');
var MongoClient = MongoDB.MongoClient;
const ObjectID = MongoDB.ObjectID;
var Config = require('./config.js');

class Db {
	static getInstance() { /*1、单例  多次实例化实例不共享的问题*/
		if (!Db.instance) {
			Db.instance = new Db();
		}
		return Db.instance;
	}

	constructor() {
		this.dbClient = '';
		/*属性 放db对象*/
		this.connect();
		/*实例化的时候就连接数据库*/
	}

	connect() { /*连接数据库*/
		let _that = this;
		return new Promise((resolve, reject) => {
			if (!_that.dbClient) { /*1、解决数据库多次连接的问题*/
				MongoClient.connect(Config.dbUrl, (err, client) => {
					if (err) {
						reject(err)
					} else {
						_that.dbClient = client.db(Config.dbName);
						resolve(_that.dbClient)
					}
				})
			} else {
				resolve(_that.dbClient);
			}
		})
	}

	find(collectionName, json) {
		return new Promise((resolve, reject) => {
			this.connect().then((db) => {
				var result = db.collection(collectionName).find(json);
				result.toArray(function (err, docs) {
					if (err) {
						reject(err);
						return;
					}
					resolve(docs);
				})
			})
		})
	}

	update(collectionName, json1, json2) {
		return new Promise((resolve, reject) => {
			this.connect().then((db) => {
				//db.user.update({},{$set:{}})
				db.collection(collectionName).updateOne(json1, {
					$set: json2
				}, (err, result) => {
					if (err) {
						reject(err);
					} else {
						resolve(result);
					}
				})
			})
		})
	}

	insert(collectionName, json) {
		return new Promise((resolve, reject) => {
			this.connect().then((db) => {
				db.collection(collectionName).insertOne(json, function (err, result) {
					if (err) {
						reject(err);
					} else {
						resolve(result);
					}
				})
			})
		})
	}

	remove(collectionName, json) {
		return new Promise((resolve, reject) => {
			this.connect().then((db) => {
				db.collection(collectionName).removeOne(json, function (err, result) {
					if (err) {
						reject(err);
					} else {
						resolve(result);
					}
				})
			})
		})
	}

	getObjectId(id) { /*mongodb里面查询 _id 把字符串转换成对象*/
		return new ObjectID(id);
	}
}

module.exports = Db.getInstance();
// 数据库的测试
/*
var myDb = Db.getInstance();

setInterval(function() {
    console.time('start');
    myDb.find('user', {}).then(function(data) {
        // console.log(data);
        console.timeEnd('start');
    })

}, 1000)

setTimeout(function() {
    console.time('start1');
    myDb.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start1');
    })

}, 3000)

var myDb2 = Db.getInstance();

setTimeout(function() {
    console.time('start3');
    myDb2.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start3');
    })

}, 5000)

setTimeout(function() {
    console.time('start4');
    myDb2.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start4');
    })

}, 7000)*/
